1. Field of Invention
The present invention relates to a heat resistant resin film with a metal thin film used as an intermediate transferor like an endless belt, a fixing belt of a fixing unit, or the like in an image forming apparatus for forming an image with dry toner by use of an electrophotographic system, an electrostatic recording system or the like, the image forming apparatus such as a printer, a copying machine, or the like; a method for manufacturing such a heat resistant resin film; such an endless belt; a method for manufacturing such an endless belt; and such an image forming apparatus.
2. Description of Related Art
A thin film of conductive metal such as copper, aluminum, or the like, is laminated on a thin plate made of heat resistant resin, or a thin plate in which a core material made of glass fiber or the like has been impregnated with heat resistant resin. Such a laminate is hitherto used broadly as a printed wiring board. Also in an image forming apparatus such as a printer, a copying machine, or the like, for forming an image with dry toner by use of an electrophotographic system, an electrostatic recording system or the like as described above, a film in which a heat resistant resin film and a metal thin film have been laminated on each other and which has been formed into an endless shape is sometimes used as an intermediate transferor or the like, which is transferred a dry toner image formed on an image carrier such as a photoconductor drum and holds the toner image temporarily.
An electrostatic latent image is formed on the photoconductor drum and toner is made to adhere to the electrostatic latent image. Thus, the electrostatic latent image is developed by toner and then transferred onto the endless intermediate transferor. Then, in the endless intermediate transferor having the toner image transferred thereon, the metal thin film laminated onto the heat resistant resin is made to generate heat by use of an electromagnetic induction effect. Thus, the toner image transferred onto the intermediate transferor is heated so that the toner image is transferred and fixed simultaneously on a recording medium which is pressed onto the intermediate transferor at predetermined timing.
A schematic configuration of such an image forming apparatus will be described next.
FIG. 12A is a schematic configuration view showing the above-mentioned image forming apparatus. This image forming apparatus is a full-color laser printer using an electrophotographic system. FIG. 12B is an enlarged view showing a main portion of the same image forming apparatus. This image forming apparatus has a photoconductor drum 101 on a surface of which a latent image based on a difference in electrostatic potential is formed. Around the photoconductor drum 101, the image forming apparatus has a charging unit 102 for charging the surface of the photoconductor drum 101 substantially uniformly; an exposure section for irradiating the photoconductor drum 101 with laser light in accordance with signals of respective colors of cyan, magenta, yellow, black, and so on, so as to form an electrostatic latent image on the photoconductor drum 101, the exposure section provided with a laser scanner 103, a mirror 104 and so on; a rotary developing unit 105 for storing toners of four colors of cyan, magenta, yellow and black respectively, and visualizing the electrostatic latent image on the photoconductor drum 101 with the respective color toners; an intermediate transferor 106 supported movably circularly in a fixed direction and shaped like an endless belt; a cleaning unit 107 for cleaning the surface of the photoconductor drum 101 after the transfer; and an exposure lamp 108 for removing charge from the surface of the photoconductor drum 101.
The endless intermediate transferor 106 is stretched around a driving roller 110 and a tension applying member 111. A pressure roller 112 is provided to press the driving roller 110 through the intermediate transferor 106. An electromagnetic induction heating unit 113 for heating the intermediate transferor 106 is provided on an upstream side of a position where the driving roller 110 and the pressure roller 112 are opposed to each other, in the moving direction of the intermediate transferor 106.
Further, a paper feed roller 116 and a registration roller 117 both for carrying, one by one, a recording material which is stored in a paper feed unit 115 and a recording material guide 118 for feeding the recording material between the intermediate transferor 106 and the pressure roller 112 are provided in the image forming apparatus.
The electromagnetic induction heating unit 113 has an exciting coil 113a to generate an alternating magnetic field passing through the intermediate transferor 106, as shown in FIG. 13. On the other hand, the intermediate transferor 106 has a base layer 106a, a conductive layer 106b (electromagnetic induction heating layer) laminated on the base layer 106a, and a releasable layer 106c superior in releasability. An eddy current B is generated in the conductive layer 106b by the alternating magnetic field. The conductive layer 106b generates heat due to the eddy current B so as to heat and melt the toner image carried on the surface of the intermediate transferor 106.
In such an image forming apparatus, the respective color toner images formed on the photoconductor drum 101 are transferred sequentially onto the intermediate transferor 106 by a bias voltage applied between the photoconductor drum 101 and the driving roller 110, so as to be superimposed on one another. Thus, a full-color toner image is formed. The conductive layer 106b of the intermediate transferor 106 is heated by electromagnetic induction so that the toner image is melted. The melted toner image is superimposed on a recording material, and subjected to compression bonding to the recording material between the pressure roller 112 and the driving roller 110. Thus, the toner image is transferred to the recording material and fixed thereon simultaneously.
For example, a film-like member having a thickness of 50 to 200 μm and made of heat resistant resin such as thermosetting polyimide, aromatic polyamide (aramid), liquid crystal polymer, or the like and a copper thin film having a thickness of about 1 to 50 μm are laminated on each other to form an endless belt, and the endless belt is used as the intermediate transferor 106.
As methods for manufacturing a film-like member in which a heat resistant resin layer and a metal thin film have been laminated on each other as mentioned above, there have been known a method in which a heat resistant resin film and a sheet of metal foil are bonded with each other by an adhesive agent or the like; a method in which a metal thin film is formed on a heat resistant resin film by means of electrolytic plating, electroless plating, vapor deposition, or the like; and so on.
However, in the method in which a heat resistant resin film and a sheet of metal foil are bonded with each other by an adhesive agent or the like as mentioned above, there is a problem that not only is the process of work complicated, but reliability is also lacked in the bonding force between the heat resistant resin film and the sheet of metal foil when the metal thin film is heated repeatedly by electromagnetic induction.
On the other hand, also in the method in which a metal thin film is formed on a heat resistant resin film by means of electrolytic plating, electroless plating, vapor deposition, or the like, there is a problem that heat resistant resin such as polyimide or aromatic polyamide (aramid) is generally high in surface energy so that the bonding property deteriorates and hence it is difficult to make the heat resistant resin firmly adhere to the metal thin film of copper or the like.
Therefore, for example, JP-A-Hei. 5-299820, JP-A-Hei. 6-316768, JP-A-Hei. 7-216225, JP-A-Hei. 6-256960, and so on, disclose techniques for solving such problems and improving the bonding property between the heat resistant resin and the metal thin film.
JP-A-Hei. 5-299820 proposes the following technique. That is, a metal deposited film is formed on polyimide. Then, a copper layer based on electron beam heating deposition and a copper layer based on electrolytic plating are laminated on the metal deposited film sequentially.
Moreover, JP-A-Hei. 6-316768 discloses the following technique. That is, polyimide is impregnated with fluororesin in advance. In order to make the fluororesin a bonding site, a first stage of etching treatment is first carried out with a water solution containing hydrazine, and succeedingly a second stage of etching treatment is carried out with naphthalene-1-sodium so as to make it easy for copper to adhere thereto.
Further, JP-A-Hei. 7-216225 discloses the following technique. That is, metal powder is mixed into a precursor of polyimide in advance. Thus, the bonding property with a metal film based on plating is enhanced.
Furthermore, JP-A-Hei. 6-256960 proposes the following technique. That is, even if the heat resistant resin is aromatic polyamide (aramid), etching treatment is carried out with a water solution containing hydrazine and alkali metal hydroxide. Succeedingly, catalyst applying treatment for electroless plating is carried out.
However, the above-mentioned techniques according to the related art have problems as follows. That is, in each of the techniques disclosed in JP-A-Hei. 5-299820, JP-A-Hei. 6-316768, JP-A-Hei. 7-216225, JP-A-Hei. 6-256960, and so on, chemical treatment or the like is applied to the surface of heat resistant resin to form a metal thin film after the heat resistant resin is molded. In these methods, however, there has been a problem that a sufficient bonding property cannot be obtained between the heat resistant resin and the metal thin film, or the process of the chemical treatment is complicated so that it is difficult to rationalize the manufacturing process.